Irva Hertz-Picciotto & colleagues have published results of a study comparing
mercury (Hg) levels in children with and without autism (1). The study does not
report findings about total body burden of Hg in children, nor does the study
evaluate levels of Hg in the brain or other specific organs in autistic and
non-autistic children.

Indeed, the researchers who did the blood-Hg study state: "As only 5% of body
burdens of Hg are estimated to be in circulation, (Burbacher et al. 2005;
Stinson et al. 1989) reliable conclusions about distribution are not possible
from one-time observational measurements in blood." (1) Since various forms of
mercury can enter the brain and remain there (17), and since different tissues
of humans and other species retain mercury at various rates (16), the larger
context of Hertz-Picciotto et al's findings need be considered.

Relevant questions include: What do Hg levels in blood signify? Alternatively,
what don't they signify? And what does intra-body and intra-brain mercury mean
for children with weak alleles in glutathione-related pathways or born to
mothers with weak alleles in glutathione-related pathways?

Although the new study purports to offer a review of autism genetics, Hertz-Picciotto
et al (1) omit an important category of citations related to mercury,
glutathione, methylation, and autism (eg, 2-14).

Furthermore, the researchers cite two studies of in vivo thimerosal levels (Pichichero
et al 2002, 2008) while omitting consideration of Waly et al 2004, who
investigated thimerosal levels lower than those described by Pichichero et al
2002 in human infants, found that methionine synthase was inhibited, and
concluded that "The potent inhibition of this pathway by ethanol, lead, mercury,
aluminum and thimerosal suggests that it may be an important target of
neurodevelopmental toxins." (15)

Why were these important findings omitted? Weren't the reviewers aware of cites
1-15 hereinbelow?

In a study available free online, data reviewed by Lorscheider et al (16)
indicate that Hg exposure does not lead to equivalent concentration in all
tissues. For instance, from chronic exposure via amalgam vapors, some tissues
accumulate more Hg than do other tissues (16).

Caveat: ingesting one's own amalgam vapors probably includes olfactory exposure
as well as oral/gastrointestinal exposure and therefore is not perfectly akin to
ingesting Hg by eating fish. Nonetheless, Hg distribution findings due to
amalgams may be instructive.

"The degree to which body tissues can sequester amalgam Hg after exposure has
been demonstrated in a variety of human and animal experiments... The brain/CSF
Hg ratio had increased threefold by 4 wk after amalgam fillings had been
installed..." (16)

"Repeated observations in adult sheep... demonstrate that after placement of
amalgam fillings the blood Hg levels remain relatively low even though the
surrounding body tissue concentrations of Hg become many fold higher than blood.
This suggests that tissues rapidly sequester amalgam Hg at a rate equivalent to
its initial appearance in the circulation. Such a phenomenon may explain why
monitoring blood levels of Hg in humans is a poor indicator of the actual tissue
body burden directly attributable to continuous low-dose Hg exposure from
amalgam." (16)

Lorscheider et al (16) summarize another important point:

"Both intracellular Hg2 and Hg are ultimately bound covalently to glutathione (GSH)
and protein cysteine groups. Hg2 is the toxic product responsible for the
adverse effects of inhaled Hg0. Body tissues have various retention half-lives
for Hg and Hg2 ranging from days to years... "

Implications ensue from the Hg/GSH genetics findings in autism and from the
Hg-distribution studies reviewed in Lorscheider et al:a) Tissue levels of Hg are are likely
differ from and to be greater than Hg levels found in blood. b) Subgroups of children who have
developed autism are known to have one or more problems in pathways related to
glutathione and methylation (eg, 2-14) may detoxify Hg and related compounds
poorly and thus may sequester Hg and related compounds disadvantegeously. c) Blood levels of Hg in autistic
children (1) tell us little about Hg in their brain and other tissues.

As Hertz-Picciotto et al mention, several studies have found associations
between autism rates and environmental mercury (18-20), and these findings
conjoin with the often ignored fact that thimerosal in early life vaccines
increases risk for autism and for developmental disabilities requiring special
education (21-22).